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M. G. KELLOGG. MULTIPLE SWITGHBOARD.

No. 592,315. 01 Patented Octvz26, 1897.

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Nrrnn STATES MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TOTHEKELLOGG S\VITCIIBOA RD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,315, dated October26, 1897.

Application filed November 29, 1889. Serial No. 332,018. (No model.)

To all whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Ohicago,Illinois,temporarilyresiding at Stuttgart,in the Empire of Germany, have invented certainnew and useful Improvements in M ultiple Switchboards forTelephone-Exchanges, of which the following is a full, clear, concise,and exact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to a telephone-exchange system in which thesubscribers lines are metallic-circuit lines; and it consists inapparatus and a system of testing at any board of an exchange todetermine whether a line is in use at another board.

In the accompanying drawings, illustrating my invention, Figures 1 and 1are front views of sections of two multiple switchboards to which thesame lines are connected. Fig. 2 shows a complete diagram of boards withtheir connections and all the central-office apparatus, circuits, andconnections necessary to illustrate my invention.

In the drawings like parts and apparatus are indicated by the sameletters of reference.

In Fig. 2, A is a sectional view of the switchboard shown in Fig. 1, andA is a sectional View of the switchboard shown in Fig. 1*, each asindicated by the line cl e. I place as many boards in the central ofiiceas are found necessary or desirable in order to answer the calls andmake the connections. On each board is a spring-jack or other switch foreach line. Each switch has a contact-spring which normally bears on aninsulated contact-point and has another contact-piece insulated from therest (except by the circuit connections) and is adapted to receive aloop-switch plug and, when a plug is inserted, to disconnect the springfrom the contact-point and connect the contact-pieces of the plug withthe spring and said insulated contact-piece of the switch, respectively.

The switching apparatus of a line on the board where its calls are to beattended to is different from and is connected differently At this boardthe line terwhen it is not switched to connect its line forconversation) placed in a switching device adapted to connectelectrically the two contact-pieces of the plug. This switching devicehas also contact-pieces which are separated by the insertion of the plugand are in contact when the .plug is not inserted.- One of them isconnected to the line and the other is connected to one side of all thetest receiving instruments of the boards. The pairs of switchpoints orpieces of a line which are normally in contact are placed in circuit inone of the sides or branches of the line and between the contact-pieceof the switch-plug and the subscribers station, and are so connected inthe circuit that when aswitch-plug of one lineis inserted into anyswitch of another line it disconnects the saidside or branch of thesecond line from said contact-piece of the plug of the second line andconnects said side or branch with one of the contact-pieces of the plugwhich is inserted; The other branch of the line is connected at eachboard to a contact-piece suitably placed and with which a switch testingplug or device connected to the other side of a test receivinginstrument from that mentioned above is adapted to be brought intocontact. The side or branch of the line last mentioned is also connectedat its switch at each board to a contact-piece suitably placed andadapted to be in connection with the other contactpiece of a switch-plugwhen it is inserted into the switch. The contact-pieces to which thetest-plu g is applied and these switch contactpieces may be one and thesame piece, as shown.

On each board I place in convenient positions one or more switchingdevices, each having two contact-pieces, with which the operator at willmay bring into contact the two contact-pieces, respectively, of anyloop-plug located at her board. At each board I also place in convenientpositions switching devices adapted to loop a calling-generator and anoperators telephone into the circuit of any line which has its loop pluglocated at the board.

In Fig.

to the switches and apparatus on the two 2 of the drawings twometallic-cir .cuit lines are shown, and they are connected boards insuch a manner as to allow all the necessary operations of an exchangesystem and show theprinciples of my invention. The two sides of one lineare marked line No. 1 and line No. 1".

jack switches for this line. The two sides of the other line are markedline No. 2 and linev N0. 2". s and s are the two springjack switches ofthis line.

a b are the rubber strips onwhich the metal parts of the switches aremounted.

g g are the spring contact-pieces of the Y which are its pairs ofcontact-points.

0 0 are'the switching devices in which the plugs are normally placed g gare contact-springs connected to their .respective lines. Contact-pointsh h, on

whichv these contact-springs rest when their plugs are not in theswitching devices, are

connected to one side of each of the test receivinginstruments.Thepieces j j are connected with their corresponding springs g g. Thereis one switching device for each line, and it is located at the boardwhere the double plug of the line is located, and the plug is normallyin position in the switching device whichbelongs to its line.

to and 0c are calling-annunciators for the two lines.

D and D are two loop-plugs attached to double flexible cords, D beingfor line No. 1 and D for line No. 2.

W and X are looping-in switches forthe lines, connected to theircircuits and to the other apparatus substantially as shown.

B B are calling generators or batteries, and ttare operators telephones.There should be one looping-in switch for each line, each at the boardwhere the calls of the line are to be answered, and they should beconnected to the operators telephone,calling-generator, and to the line,substantially as shown and as will be apparent to those skilled in theart.

J J at the two boards are test-plugs adapted to be brought intoconnection with the pieces jj at their respective boards.

25 t are test receiving instruments, and B is a test-battery. One sideof the test-battery is connected by metallic connection with thecontact-pieces h h of all the switching devices of the exchange. Eachtest receiving instrument is connected on one side to its test-plug andis connected on its other side r and r are the two spring,

of the boards and are adapted at the will of the operator to be broughtinto connection with the two contact-pieces of any loop-plug at theirboard.

The main-lineconnections are substantially as shown, and, as heretoforeindicated, usual forms of apparatus may be used at the subscribersstations.

The operation of the system is as follows: When a subscriber operateshis generator, the annunciator of the line indicates a call. Theoperator then removes the line-plu g from its switching device and,placing'it to her .switch device 0, finds out by conversation what lineis wanted. She should leave the plug in the switching device 0 or 0 andaccomplish the same result by means of the switch W or X, as will beplain on tracing the circuit. She then tests the line wanted and if shefinds it tests free she places the loop-plug in the spring-jack of theline. The two lines are thereby connected together in metallic circuit,and the operator can by moving the looping-in switch 'of the calling-.line send a calling-current or loop her tele- It will be seen thatphone into the circuit. when the lines are thus connected theannunciator of the line whose plug is used is in their circuit and theannunciator of the other lineis not in their circuit.

The testing system is as follows: It will be noticed that when theloop-plug of any line is removed from its normal position in itsswitching device the line is connected with one side of all the testreceiving instruments (at g) and that when the plug is inserted thisconnection is broken. When the operator thereupon inserts the plug intothe switch of another line, that line is also brought into similarconnection with the test receiving instruments. When an operator at anyboard applies her test-plug to the contact-piecej of either line thusconnected, there will be a complete circuit established, in which is hertest receiving instrument and a battery, and her instrument willrespond. If, however, when she tests a line it is not switched forconversation, (either by its loop-plug having been taken from its normalposition or by the loop-plug of another line being in one of itsswitches,) the line is not connected with the side of the test receivinginstrument opposite to the test-plug, and there being no completecircuit the instrument will not respond. The operator can thereforedetermine whether or not the line is switched for use.

The test-circuit may be traced as follows: Assume, for instance,that theplug D has been inserted into switch 8 of line 2 2 at board A and that.the operator at board A desired to test the said line. The test-plug Jis brought contact h of said switch to opposite pole of test-battery.

I claim as my invention and desire to secure by Letters Patent- 1. In atelephone-exchange system, a testbattery, two metallic-circuit linesnormally disconnected from said battery, a double or loop-switch plugfor-one of said lines the two con tact-pieces of which are connected tothe two sides or branches of its line, respectively, a line-switch forthe other of said lines adapted to receive said plug and when the plugis inserted to connect the two contact-pieces of the plug with the twosides or branches, respectively, of the line to which the switchbelongs, and a switching device for said plug in which it is normallyplaced, said switching device having two contactpoints which aredisconnected when the plug is inserted and electrically connected whenthe plug is withdrawn, one of said contactpoints being connected withthe line to which the plug belongs and the other one being con nectedwith one side of said test-battery but not through the ground, incombination with a switch testing device connected on the other side ofsaid test-battery and adapted, at the will of the operator, to bebrought into connection with either line, and a test receivinginstrument in the test-circuit thus established, substantially as setforth.

2. In a telephone-exchange system, a testbattery, a metallic-circuitline normally disconnected from said battery, the two sides or branchesof which are connected to the two contact-pieces, respectively, of adouble or loop-switch plug, another metallic-circuit line also normallydisconnected from said battery and having a line-switch adapted toreceive said plug and when the plug is inserted to connect the twocontact-pieces of the plug with the two sides or branches, respectively,of the line to which the switch belongs and thereby connect the twolines together for conversation, and a switching device withcontact-points to connect the circuit of said lines with one side ofsaid test-battery but not through the ground when they are thusconnected for conversation and not otherwise, in combination with aswitch testing device connected on the other side of saidtest-batteryand adapted, at the will of the operator, to be brought intoconnection with pieces of which are connected to the two sides orbranches of its line, respectively, a lineswitch for the other of saidlines adapted to receive said plug and when the plug is inserted toconnect the two contact-pieces of the plug with the two sides orbranches, respectively, of the line, to which the switch belongs, and aswitching device with two contact-points normally separated but incontact when the lines are switched for conversation, one of said pointsbeing connected to one of said lines and the other point being connectedto one side of said test-battery but not through the ground, incombination with a switch testing device connected to the other side ofsaid test-battery and adapted, at the will of the operator, to bebrought into connection with either line, and a test receivinginstrument in the circuit thereby established, substantially as setforth.

4. In a telephone-exchange system, a local ungrounded test wire orcircuit containing a test receiving instrument and a test-battery, incombination with two metallic-circuit lines normally disconnected fromsaid test wire or circuit, a double or loop plug the two contactpiecesof which are connected to the two sides or branches of one of saidlines, a line-switch for the other line adapted to receive said plug andwhen the plug is inserted to connect the two contact-pieces of the plugwith the two sides or branches of said other line and connect the twolines together for conversation, a switching device in which said plugis normally placed, adapted on the withdrawal of the plug from it toconnect electrically the line to which the plug belongs with one end ofsaid test wire or circuit, and a switch testing device adapted, at thewill of the operator, to connect said test wire or circuit at its otherend to either of said lines, substantially as set forth.

5. In a telephone-exchange system, a local ungrounded test wire orcircuit containing a test receiving instrument and a test-battery, incombination with two metallic-circuit lines normally disconnected fromsaid test wire or circuit, a double or loop plug the two contactpiecesof which are connected to the two sides or branches of one of saidlines, a line-switch for the other line adapted to receive said plug andwhen the plug is inserted to connect the two contact-pieces of the plugwith the two sides or branches of said other line and connect thetwolines together for conversation,- a switching device with contact-pointsto electrically connect the circuit of the two lines when they are-thusconnected together with one end of said test wire or circuit, and aswitch testing device adapted, at the will of the operator, to connectsaid test wire or circuit, at its other end, to either of said lines,substantially as set forth.

6. In a telephone-exchange system, metallie-circuit lines each normallydisconnected from one side of a test-battery and having its two sides orbranches connected to the two contact-pieces respectively of aloop-switch plug adapted to be placed in the switch of any other lineand when so placed to connect the two contact-pieces of the plug withthe two sides or branches of such other line, in combination with aswitching device for each plug, into which the plugis normally placed,

contact points and connections by which itsline is automaticallyconnected with such side of said test-battery by the withdrawal of theplug from its device, a test plug or device connected to the other sideof said test-battery and adapted to be brought for testing intoconnection with either of said lines and a test receiving instrument inany circuit thereby established on testing, substantially as set forth.

7 In a telephone-exchange system, metallic-circuit lines and loop-switchplugs, one for each line, to the two contact-pieces of which areconnected, respectively, the two sides or branches of the line, incombination with a test-battery, a switching device for each line, intowhich the plug of the line is normally placed, said switching devicecontaining two contact-pieces which are out of contact when the plug isin the device but are automatically closed to each other by thewithdrawal of the plug, one of said contacts being connected to the lineand the other to one side of said test-battery, a plug connected to theother side of the battery and adapted to be brought for testing intoconnection with the line and atest receiving instrument in thetest-circuit thereby established on testing, substantially as set forth.

8. In a telephone-exchange system, electric circuits and switch-plugs,one for each circuit, in combination with a test-battery, a switchingdevice for each circuit, into which the plug of the circuit is normallyplaced, said switching device containing two contact-pieces which areout of contact when the plug is in the device but are automaticallyclosed to each other by the withdrawal of the plug, one of said contactsbeing connected to the circuit and the other to one side of saidtest-battery, a plug connected to the other side of the battery andadapted to be brought for testing into connection with the circuit and atest receiving instrument in the testcircuit thereby established ontesting, substantially as set forth.

9. In a telephone-exchange system,-a local test wire or circuitcontaining a test receiving instrument and a test-battery in combinationwith two metallic-circuit lines normally disconnected from said testwire or circuit, a double or loop plug the two contact-pieces of whichare connected to the two sides or branches of one of said lines, aline-switch for the other line adapted to receive said plug and when theplug is inserted to connect the two contact-pieces of the plug with thetwo sides or branches of said other line and connect the two linestogether for conversation, a switching device in which said plug isnormally placed, adaptedv on the withdrawal of the plug from it toconnect electrically the line to which the plug belongs with one end ofsaid test wire or circuit, and aswitch testing device adapted at thewill of the operator, to connect said test wire or circuit at its otherend to either of said lines, substantially as set forth.

10. In a telephone-exchange system, a local test wire or circuitcontaining a test receiving instrument and a test-battery, incombination with two metallic-circuit lines normally disconnected fromsaid test wire or circuit, a double or loop plug, the two contact-piecesof which are connected to the two sides or branches of one of saidlines, a line-switch for the other line adapted to receive said plug andwhen the plug is inserted to connect the two contact-pieces of the plugwith the two sides or branches of said other line and connect the twolines together for conversation, a switching device with contact-pointsto electrically connect the circuit of the two lines when. they are thusconnected together with one end of said test wire or circuit, and aswitch testing device adapted at the will of the operator, to connectsaid test wire or circuit, at its other end, to either of said lines,substantially as set forth.

11. In a telephone exchange multipleswitchboard system, ametallic-circuit line, a loop-switch plug for said line in the twocontact-pieces of which the two sides or branches of the linerespectively terminate, and a switching device in which said plug isnormally placed, said device having electricallyconnectedcontact-pieces, with which the two contact-pieces of the plug makecontact to electrically connect or bridge the contactpieces of the plugwhen it is inserted therein, and a contact against which aline-connected contact bears, when the plug is withdrawn,

to connect the line with one side of a test' receiving instrument,substantially as set forth.

12. [n a telephone-exchange multipleswitchboard system, ametallic-circuit line, a loop-switch plug for said line in the twocontact-pieces of which the two sides or branches of the linerespectively terminate, and a switching device in which said plug isnormally placed, said device having means for electrically connecting orbridging the two sides of the line when the plug is in its normalposition therein and a contact against which a line-connected contactbears, when the plug is withdrawn from the switching device, to thenconnect the line with one side of a test receiving instrument,substantially as set forth.

In witness whereof I hereunto subscribe my name this 1st day of October,1889.

-MILO G. KELLOGG'.

Witnesses: v

FRANCES D. KELLOGG, MARGARETHA RIEI-IL.

